1. Field of the Invention
The present invention relates to a disc cartridge loading mechanism and, more particularly, to a loading mechanism for a magnetic disc storage system of the type incorporating a removable disc cartridge which provides for positive control against external contamination entry into the head flying environment.
2. Description of the Prior Art
Magnetic disc storage systems are widely used to provide large volumes of relatively low-cost, computer-accessible memory or storage. A typical disc storage device has a number of discs coated with a suitable magnetic material mounted for rotation on a common spindle and a set of transducer heads carried in pairs on elongated supports for insertion between adjacent discs, the heads of each pair facing in opposite directions to engage opposite faces of adjacent discs. The support structure is coupled to a positioner motor, the positioner motor typically including a coil mounted within a magnetic field for linear movement and oriented relative to the discs to move the heads radially over the disc surfaces to thereby enable the heads to be positioned over any annular track on the surfaces. In normal operation, the positioner motor, in response to control signals from the computer, positions the transducer heads radially for recording data signals on, or retrieving data signals from a pre-selected one of a set of concentric recording tracks on the discs.
The transducer heads are supported above the disc surfaces by a film of air to prevent contact therebetween which might otherwise damage one or both members. Modern magnetic disc drives incorporate rigid substrate discs, the surfaces of which are polished to a high finish so that the heads can reliably fly on the air bearing. Systems are presently being developed wherein the heads fly above the disc recording surfaces at heights of less than 20 microinches.
In such a magnetic disc drive, it is extremely important to control the cleanliness of the head flying environment. The presence of contamination particles on a disc may effect the flight attitude of the heads and thereby reduce their ability to record and retrieve data from the disc surfaces. In the extreme, the presence of disc contamination may cause a crash of a flying head, causing destruction of the head and/or disc.
Accordingly, a typical magnetic disc drive incorporates a filtered air system to control cleanliness of the head flying environment. It is very common in disc pack drives or disc cartridge drives to incorporate a purging cycle, wherein the disc is brought up to rotationaal speed and some period of time is spent with the disc rotating in the presence of a filtered air flow before the heads are moved into proximity with the disc.
In fixed disc systems, it is relatively easy to maintain cleanliness of the head flying environment. On the other hand, there is presently a strong market demand for media removability. Accordingly, rigid discs presently are sold in data cartridges which incorporate various features to protect the media for flight. Drives configured to make use of this type of cartridge incorporate, in general, certain features. A front door is incorporated that allows insertion of the cartridge. When this door is open, the volume containing the flying heads is generally exposed to the outside environment of the drive, thereby exposing the heads and their support structure to contamination while the cartridge is inserted.
To protect the disc in the cartridge when it is external from the machine, the disc typically includes a plurality of doors which are normally closed to the outside environment. The cartridge also includes an opening for receipt of a puch rod which, when inserted in this opening, opens the doors. In a typical disc cartridge drive, as the cartridge is pushed into the drive, a stationary push rod enters the door mechanism opening to open the sliding door to allow for entry of the heads during drive operation. This door opening occurs well before the cartridge is fully seated. Accordingly, this technique opens the cartridge to the previously contaminated drive environment, allowing contamination to enter the cartridge. As a result, previous disc cartridge drives have presented problems in the area of long term product reliability.